Vice President Biden and his Republican opponent, Rep. Paul Ryan of Wisconsin, had a lively debate at Centre College in Danville, Ky., this evening — one marked by Biden's aggressive challenges to many of the Republican vice presidential nominee's claims and Ryan's oft-repeated message that the Obama-Biden administration's policies aren't working.

The discussion was steered by ABC News' Martha Raddatz. It's the only vice presidential debate of the campaign.

There were disputes about the response to last month's attack on the U.S. Consulate in Benghazi, Libya, how to keep Iran from obtaining nuclear weapons, health care policy and taxes, and over which ticket has the better plan for getting the economy moving.

Both candidates, NPR Senior Washington Editor Ron Elving said afterward, "were strong and they were strong in the way that they wanted to be strong." Ryan "made the Romney-Ryan case" and Biden came back "point for point."

Much was at stake. Last week's presidential debate, which we live blogged, is widely seen as having given a bump to the Republican ticket, headed by former Massachusetts Gov. Mitt Romney. Polls show most Americans who watched that debate thought he did a better job than President Obama.

We updated before and during the debate. We'll do the same during next Tuesday's second debate between the president and Romney.

Update at 10:35 p.m. ET. In Closing, Biden Talks Of Those Who Just "Want A Shot"; Ryan Talks Of "A Clear Choice":

In his closing statement, Biden returns to Romney's comments about the "47 percent" and to Ryan's having said that 30 percent of Americans "are takers."

"He's talking about my mother and father," Biden says, and "the people who built this country. All they're looking for is a shot. ... The president and I are not going to rest until the playing field is level."

Ryan uses his closing to talk about "the clear choice" he says voters have between the current administration that promotes "more spending, more borrowing, higher taxes and a government takeover of health care. ... It's not working."

Update at 10:28 p.m. ET. "Attack, Blame And Defame":

Raddatz wants to know what the men would say to a veteran who is upset at the tone of the campaign.

Biden says both sides have said things they probably regret, but that he would also want to assure that veteran that Obama is a president who has "acted wisely in the use of force" while Romney has been guilty of "slipshod comments" about foreign affairs.

Ryan talks of Obama as being a president who promised "hope and change" but has instead "turned this campaign into attack, blame and defame." Another ALERT? (a Line Everybody [will] Remember Tomorrow).

Update at 10:22 p.m. ET. Abortion:

Raddatz asks the men to talk personally about their positions on abortion.

Ryan talks of his belief that life begins at conception and says the policy of a Romney-Ryan administration will be to oppose abortion except in cases of rape, incest or a threat to the life of the mother.

Biden says he accepts the Catholic Church's teaching on abortion, but also that "I refuse to impose it" on others.

Update at 10:12 p.m. ET. Statements Are Not Going Unchallenged, Particularly By Biden:

President Obama was criticized, even by some of his supporters, for not challenging Romney during last week's debate. Biden is not going to get similar criticism. He's been interrupting Ryan and challenging statements throughout the debate. Moments ago, for example, Ryan said there aren't enough U.S. troops in eastern Afghanistan. "You'd rather Americans be going in to do the job?" Biden interjected. "We're sending in more Afghans to do the job."

Ryan has been taking a slightly different approach. He's been less focused on challenging Biden's claims and more focused on making sure he gets certain messages across. Notably, he's said several times that the Obama foreign policy is "unraveling" and leading other nations to believe America is weakening.

Update at 10:05 pm. ET. On Afghanistan, Some Agreement:

Ryan says the Republican ticket agrees with the administration's goal of having all U.S. combat troops out of Afghanistan in 2014. One area of disagreement, he says, is that "we would have more likely taken into account recommendations from commanders" about troop levels this year and not withdrawn the "surge" troops as quickly as they have been.

Biden speaks plainly about the plan. "We are leaving, we are leaving in 2014, period," he says. Republicans, he adds, want to add a clause that withdrawal of troops "depends" on conditions. "It does not depend on us," says Biden. American troops will be out of the country by then no matter what.

Update at 9:55 p.m. ET. Taxes:

Raddatz asks each candidate who would pay more and who would pay less in taxes if they are elected?

Biden says under Obama-Biden the "middle class will pay less and people earning $1 million" will pay more.

Ryan doesn't directly answer. When Raddatz presses for specifics on the Romney-Ryan tax plan, he responds that voters should "look at what Ronald Reagan and Tip O'Neill did" — in other words, that a Romney-Ryan administration would work across party lines but doesn't want to lay out specifics now.

The two disagree on whether simply cutting taxes can boost job growth. Ryan says it happened under President Kennedy. "Oh, now you're Jack Kennedy!" Biden responds with a shocked look. That could be another ALERT (a Line Everybody [will] Remember Tomorrow).

Update at 9:43 p.m. ET. Repeating The $716 Billion Debate:

Ryan repeats a charge that has come up again and again during the campaign: that Obamacare takes $716 billion out of Medicare. "They got caught with their hands in the cookie jar," he says.

Not true, responds Biden, who says "we cut the cost of Medicare and stopped overpaying" to providers and insurers. The Obama plan, he says, "extended the life of Medicare to 2024." The Romney-Ryan plan, he argues, would make Medicare insolvent in 2016.

Update at 9:30 p.m. ET. A Zinger About Biden's Gaffes:

After Biden's comments about what Romney said concerning the "47 percent," Ryan gets off an ALERT (a Line Everybody [will] Remember Tomorrow). The vice president surely knows, Ryan says, that "sometimes the words don't come out of your mouth the right way." That indirect reference to the vice president's penchant for gaffes gets a big laugh from the audience.

Says Biden: "But I always say what I mean."

Update at 9:27 p.m. ET. The 47 Percent Gets Its Mention:

At last week's presidential debate, President Obama never mentioned Romney's comments about the "47 percent" who don't pay income taxes and won't support the Republican ticket.

Biden dives right into the subject after Raddatz asks about the economy and jobs.

After saying the Obama administration will get the jobless rate under 6 percent in a second term, Biden says "I've had it up to here with this notion that 47 percent" of Americans aren't doing their share. Instead of pledging not to ever raise taxes, he says, Republicans should be "signing a pledge to the middle class that we're going to level the playing field."

Ryan responds that when Obama-Biden took office, the jobless rate in Biden's hometown of Scranton, Pa., was 10 percent and it's still 8.5 percent. "That's how it's going" across the nation, he says.

Update at 9:24 ET. Ryan Pushes On Iran; Biden Pushes Back:

Ryan says the Obama administration "has no credibility on the issue" of how to prevent Iran from obtaining nuclear weapons because Obama has allegedly "watered down sanctions, delayed sanctions."

"It's incredible," Biden responds. "Imagine if we had let a Republican Congress work out the sanctions. ... Do you think there's any possibility the entire world would have joined us [in] the most crippling sanctions ever?"

Ryan says "the ayatollahs" are "spinning the centrifuges faster."

Biden says all he's hearing from the Republicans is "bluster ... and loose talk." Does Ryan want war with Iran, he asks.

Update at 9:13 p.m. ET. Sharp Disagreement On Libyan Attack And What It Symbolizes:

The first question is about the Sept. 11 attack on the U.S. consulate in Benghazi, Libya, that left the U.S. ambassador and three other Americans dead.

Raddatz asks if it was a "massive intelligence failure."

Biden calls it a "tragedy" and then turns to ticking off what he sees as President Obama's foreign policy accomplishments, including the killing of Osama bin Laden.

Ryan asks why "the ambassador in Paris has a Marine unit protecting him," but the ambassador to Libya didn't. He calls the attack in Benghazi a symbol of "the unraveling of the Obama foreign policy."

Biden says "that's a bunch of malarkey" and says "the congressman, here, cut embassy security" in budgets he has proposed.

The candidates have taken their seats (they're at a table with Raddatz) and things are getting started. As we said before, there are supposed to be nine sections of roughly 10 minutes each and they'll be asked about domestic and foreign policy issues. A coin toss has determined that Biden will respond first to the initial question.

Update at 8:45 p.m. ET. Scaled-Back Expectations, Viewerwise:

Before last week's presidential faceoff, debate commission Co-Chairman Frank Fahrenkopf told the audience that "50 to 100 million" Americans would be watching. He just told the audience at tonight's event that "50 or 60 million" voters might be tuning in. Vice presidents, apparently, get lower forecasts.

The major broadcasters aren't showing it, but C-SPAN has gone live to the debate hall for the opening announcements from the officials of the Commission on Presidential Debates. So, things are getting started.

Update at 8:15 p.m. ET. What Does Each Man Need To Do?

This afternoon, NPR Senior Washington Editor Ron Elving told our Newscast Desk that that even though Ryan is a member of the House and a committee chairman there, "because he has never run statewide in Wisconsin — [and] he's never run for national office — he's going to need to show that he's ready to be seen at that level of the game."

Biden, "who's been around for quite a long time," needs to show he is "still sharp enough, still full of energy enough, is still clear-minded enough and clearsighted enough to handle this kind of debate pressure and to handle the pressure of the job of being right next door, a heartbeat away, from the Oval Office."

Update at 8:05 p.m. ET. Buzzwords And Things To Watch For:

Before nights like these, news outlets love to do lists covering what to watch and listen for. Here are three that come from different angles:

On key issues, though, they have significant differences. Biden, for instance, is an "advocate for Obama's health care overhaul, which he once advised the president to delay given harsh economic conditions." Ryan "opposes Obamacare; wrote a budget plan that secures savings by converting Medicare from a guaranteed benefits to a voucher plan, and Medicaid to a state block grant program tied to inflation."

The two men are also from different generations. Biden is 69. Ryan is 42.

Update at 7:35 p.m. ET. What's The Format?

"The debate will cover both foreign and domestic topics and be divided into nine time segments of approximately 10 minutes each," the Commission on Presidential Debates says. "The moderator will ask an opening question, after which each candidate will have two minutes to respond. The moderator will use the balance of the time in the segment for a discussion of the question."

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